Method and means for testing X-ray tubes



Aug. 5, 1941. L. F. BLACK METHOD AND MEANS FOR TESTING X- RAY TUBES,Filed Aug. 31. `1959 a. cust-nunlonnnonuosoltf/V VEN Tol? relire/c ZacPatented Aug. 5, 1941 UNITED STATES PATENT OFFICE METHOD AND MEANS FORTESTING X-RAY TUBES (Granted under the act of March 3, 1883, as amendedApril 30, 1928; 370 0. G. 757) 8 Claims.

This invention described herein may be manufactured and used by or forthe Goverment for governmentalpurposes, without rthe payment to me ofany royalty thereon.

This invention Vrelates generally to a device and method 'for examiningthe targets of X-ray tubes, but more particularly to a means and' methodfor determining the intensity of the diverging rays of said tubes atvarious angles from a central axis, at a fixed distance Vfrom the locusof emanation.

One object of the invention is to provide a device adapted to obtain apermanent record of the appearance of the .target of la Roentg-en tube.

Ano-ther object of the invention is to provide a device adapted todemonstrate the effect of angular position of the target of the Roentgentube upon :the effective ray.

A further object is to provide a means for checking the eiiecti've area,actual area and minimum projected 'area of the focal spot of a Roentgentube. is especially valuable in checkingperformance of tubes againstspecilication claims.

Still another Objectis to provide a means "for determiningthe maximumray divergence and the focal'lm distance for various types of tubes astheylare affected by the angle ofthe target face.

With'these and other objects in view this in vention relates Ito certainnovel details of construction, combination and arrangement of parts tobe more fully herein described and claimed.

Referring to the iigures,` in which like parts are designated` bysimilar reference characters:

Fig.. 1 isa front elevation of the device with the casing closed; e

. Fig. 2 is a topl plan view of the device as shown in Fig. 1,A withRoentgen :tube removed to show the holes inthe grid; Y

Fig. 3 shows a sectional viewtaken on the line 3-3'of Fig. 1, with tuberemoved; Y l Fig, .4 is a frontA elevation of the device showingthe:casing in open position with lm holder removed;

Iliig.4 5 is a plan. View of. thev arcuate grid uncurved into a flatsurface.; and

1 Fig` 6Yisf a plan view` of a` sheet 'of nlm development. i

Y The apparatus consistsv of a hollow box-like casing Iwhich may be madeof wood or any other suitable material,- and is formed in upperandllower portions II and I2 respectively, which are" connected byhinges I3 and I4 and which ai ter may be clamped in juxtaposition toeach other by latch members I5 and I6.

When the upper member or lid II is closed on the lower member or base I2the structure forms a covered box having a rectangular floor II, front`and rear Walls I8 and I9, side Walls 20 and 2|., and atop 22 having aconcave arcualte surface with sloping lateral ends 23 and 24 whichterminate at their junctions with the side walls 20 and.V ZI.

Parallel to the concave arcuate surface of the top and spaced below thesame at a predetermined riistance is cut a slit 25 which passes entirelythrough fthe boxlike structure separating the same into the base I2 andthe lid II. This slit is for the retention of a film holder, as willfurther be described.

The concave arcuate surface is formed by a ciroularly curved lead grid26 Which is provided With a centrally aligned row of equally spacedholes 2'I at right angles to its longitudinal axis, the xcenrter hole ofthe row being surrounded by holes, equal in diameter to thoseV of therow, todesignate it as the center.

On the sloping lateral ends. 23 and 24 of the upper section are affixed.uprlghts 28 andv 29 having slidably adjustable tube clamping: members30, 30 and 3l, 3|' mounted thereon` which may be fixed inV any position`along the extent of the uprights by means of the set screws 32, 32.'and 33, 33'.

The adjustable tube bracket-s` are adapted to support an X-ray tube 34so that the center of X-ray radiations from the target 35 will be at thecenter of curvature of the grid 26 and of a lm 35 which is interposedbetween the side sheets of a cardboardv iilm holder 31.

The lm holder 31 consists of two pieces of cardboard- 38 and 33 of likedimension one superimposed upon the other and hingeably connected alongthe adjoining edges of one side by` a piece of binding tape 4'0. Thesides opposite the hinged edges are held together by a latch member 4I,asl shown in` Fig. 3.

A sheet of sensitized photographic film 36 is placed `between the sheetsof cardboard and clamped thereinby the latch member 4I. Cardboard isused as cover sheets for the iii-m, since due to its iiexibility, the lmholder will readily follow the :contour of the arcuate edges of the topand bottom portions of the casing. How-` ever, any other suitableflexible material may be used for the purpose required.

In the operation ofthe device the X-ray tubo 34- is 'nrst placed betweenthe clamp members` 36, 3i and 3|, 3| and adjusted longitudinally andangularly therein, and. veiitically on the standands or uprights 28 and29, so that the center or emanating area of the target 35 on the anode43 is above the center hole 44 of the lead grid 26,

The lid or upper portion of the casing is then lifted and the lm holder3l into which a film 36 has been inserted, placed on the upper arcuateedges of the lower portion or base I2 oi the casing i0. The lid is thenclosed and latched and the tube connected to a regular X-ray energizingapparatus (not shown) through the conductors [i and d, in the usualmanner and current passed through the tube to put the same intooperation for a predetermined period, dependent on the length ofexposure desired.

After the exposure is made the energy to the tube is then cut oi and thelm holder pulled slightly through the arcuate slot between the upper andlower portion of the casing until an unexposed portion of the film isbeneath the grid holes, another tube may then be placed in the test tubebrackets `and adjusted as before and another exposure through the gridholes made. Several tubes may thus be placed in the device, one afteranother and the exposures through the grid holes photographicallyrecorded on the iilm to show the characteristic of the tube respectingits effective radiation over a predetermined angle, the condition of itstarget, etc.

v The apparatus described consists of a simple wood constructed tubeholder for the Roentgen tube with aspecial accurately perforatedleadsheet curved on an arc between the tube and a concentrically curvedlm which isexposed for record as described above, however manydeviations in the construction of the nlm holder and many iormsof gridsmay be used therewith without departing from the scope and spirit of theinvention.

The grid shown is well suited for comparison studies, as it is possibleto obtain several exposures on the same iilm.v .The tube is energizedfromv a regular X-ray machine in the usual manner.. The arc of the filmand of the lead sheet or igrid is `so constructed that the appearance ofthe iilmexposed is the same as the composite image obtained by manyhorizontally placed iilms` exposed with the target placed atvariousangles. The saving in iilm for experimental purposes in thisprocedure is obvious.

In the operation of the device the following technique is usedv inmaking the photographic records: kilovolt peak, 40; milliamperes, 10;sec. l0. The distance of the target to the lead grid may not exceed 4inches; the usual nlm distance is set by the apparatus, cardboard lmholders, as described above, are used due to their simplicty, ofconstruction, flexibility, wearing qualities and low cost. Enlargementsmay be. made by increasing thedistance to the film. The peak is retainedbelow 40 kilowatts to eliminate any danger of spark-over through thelead grid.

The photographic records made by the device will show if there arecraters or melted raised areas on the4 surface of the target by thecontour of the photographic image, orif the target is split or otherwisedefective, and the' density of the spot is a measureof the drop inkilovclt peak caused by resistance in the circuit. A comparison of thethree dierent tubes is shown by the photographic images indicated at a,b, and c, Fig. 6, which illustrate the eiectiveness of studyingpermanent photographic records in determining the qualities anddeficiencies of the various tubes.

(a) By comparison this tube appears to have a target with a platinumface and copper back. This density of the spots is not the same as inother tubes due to the drop in kilovolt peak caused by the amount ofresistance in the circuit;

(b) Shows a tube of universal medium focus, solid tungsten anode; goodcondition: Dark portion on film shows image of actual focal spot. Haloshows image of anode;

(c) Shows the image formed by a defective tube having a split target.

Having described my invention what I claim as newand wish to secure byLetters Patent is:

l. A testing device for X-ray tubes comprisingV a hollow boxlike casingformed of complementary sections composing a base and a lid, said casinghaving arcuately-shaped slotted openings between said sections, aconcave arcuatelyshaped grid concentrically arranged with respect tothecurvature of said slotted openings and forming the top of said lid,means in connection with said lid for supporting an X-ray tube abovesaid grid with its target at the center of curvature of said grid, andmeans for inclos-' ing a film to slidably mount the same within saidarcuate slots.

2. A testing device for X-ray tubes comprising a hollow boxlike casinghaving a bottom, a top, side walls, and end walls, said casing beingdivided to form complementary sections composing a base and a lid, therespective side Walls of which terminate in spaced relation to eachother to form an arcuateslot on each side of said casing, aconcave-arcuately-shaped grid concentrically arranged with respect tothe curvature of said slots and forming the top of said lid, means inconnection with said lid vfor supporting an X-ray tube above said gridwith its target at the center of curvature of said grid, and means forinclosing a lm to slidably mount the same within said arcuate slots.

3. A testing device for X-ray tubes comprising a hollow boxlike casinghaving a bottom, a

top, side walls and end. walls, said casing being divided to form'complementary sections composing a base and a lid, the respective sidewalls of which terminate in spaced relation toV Veach other to form anarcuate slot in each side Wall of said casing, means for hingeablyconnecting said lid to said base and means for latching the same inclosed position, a concave arcuatelyshaped grid concentrically arrangedywith respect to the curvature of said slots and forming the top of saidlid, means in connection with said lid for supporting an X-ray tubeabove said grid with its target at the center of` curvature of saidgrid, and. means comprising a. flexible film holder adapted to beslidably mounted within said arcuate slots. 5

4. A device of the class described comprising a base provided with atopformed of an arcuately shaped grid provided with a single arcuate rowof equally spaced exposure apertures, supports mounted upon said basefor retaining an X-ray tube with itstarget at the center of curvature ofsaid grid, and means in connection with said base for slidablysupporting aexible lm holder parallel to the curvature of; saidV grid,whereby s uccessivearcuate sections thereof may. berexposed to saidapertures.y

5. Axdevice of the class described comprising a base provided with a topformed of an arcuately shaped grid provided with a single arcuate -rowof equally spaced exposure apertures, supports mounted upon said basefor retaining an X-ray tube with its target at the center of curvatureof said grid, and within the plane of said apertures, and means inconnection with said lbase for slidably supporting an arcuate filmholder parallel to the curvature of said grid, whereby successivearcuate sections thereof may be exposed to said apertures.

6. A method of obtaining adjacently arranged photographic recordsshowing the relative effectiveness of diverging rays emanating from thetargets of X-ray tubes for comparison thereof, comprising successivelypassing rays from each of said tubes through equally spaced arcuatelyaligned exposure apertures in an arcuately shaped grid having its centerof curvature at the point of emanation of said rays, and exposin-gadjacent arcuate areas of a concentrically curved film to the rays, ofeach of said tubes, passing through said apertures.

7. A device of the class described comprising a base provided with a topformed of an arcuately shaped grid provided with exposure apertures,supports mounted upon said base for retaining an X-ray tube with itstarget at the center of curvature of said grid, and means in connectionwith said base for supporting a exible lm holder parallel to thecurvature of said grid and capable of being moved longitudinally withrespect to the axis of said grid, whereby successive arcuate sectionsthereof may be exposed to said apertures.

8. A method of obtaining adjacently arranged photographic recordsshowing the relative effectiveness of diverging rays emanating fromtargets of X-ray tubes for comparison thereof, comprising successivelypassing rays from each of said tubes through exposure apertures in anarcuately shaped grid having its center of curvature at the point ofemanation of said rays, and exposing adjacent arcuate areas of aconcentrically curved lm to the rays, of each of said tubes, passingthrough said apertures.

LAWRENCE F. BLACK.

